The invention relates to arteriography, and more particularly relates to catheters which are used in arteriography.
Such catheters are used to image arteries by injecting radio-opaque contrast material into the bloodstream. Images of the artery are formed using an X-ray camera.
To maximize the usefulness of arteriograms which are so produced, it is desirable to calibrate the images to determine, e.g. the diameter of an artery or the size of a sterosis in an artery. This presupposes an accurate knowledge of the distance between two points in the image, which distance can then be used as a gauge to calibrate the rest of the image.
It is known to use points along the catheter as such a gauge. This is done by providing two X-ray opaque bands of known spacing from each other. This produces two identifiable points in the image. Where the catheter is parallel to the image intensifier of the X-ray unit, this method works well because the apparent spacing between the points is then an accurate gauge for calibrating the image.
However, the catheter may not be parallel to the image intensifier unit. As a result, the observed distance between the two bands on the catheter image is not an accurate measure by which to calibrate the rest of the image, because the clinician does not know the relative angle between the catheter and the image intensifier and therefore does not know how much shortening of the distance between the bands in the image has taken place.
It would be advantageous to provide a means whereby arteriograms could be accurately calibrated.
One object of the invention is to provide a device which can be used to calibrate catheter arteriograms.
Other objects are to provide a device which makes it possible to calibrate catheter arteriograms in a simple and convenient manner, and in general to improve on known devices used in arteriography.